Oxygen conserving device utilizing a radial multi-stage compressor for high-pressure mobile storage

ABSTRACT

An apparatus and process for supplying low pressure oxygen-enriched gas to a patient and at a moderate pressure to a radial compressor, whereupon it is compressed and fed to a high pressure storage tank. The oxygen-enriched gas is prioritized so that it is continuously supplied via a patient flow line to the patient.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/952,763, filed Sep. 14, 2001, for Oxygen conserving device utilizinga radial multi-stage compressor for high-pressure mobile storage, whichis a continuation-in-part of U.S. Ser. No. 09/695,612, filed Oct. 24,2000 for Oxygen Conserving Device Utilizing a Radial Multi-StageCompressor for High-Pressure Mobile Storage, which in turn is acontinuation-in-part of pending U.S. Ser. No. 09/154,442, filed Sep. 16,1998 for Apparatus and Method for Forming Oxygen-Enriched Gas andCompression Thereof for High Pressure Mobile Storage Utilization, whichin turn is a continuation-in-part of U.S. Ser. No. 08/942,063, filedOct. 1, 1997, now U.S. Pat. No. 5,988,165 for Apparatus and Method forForming Oxygen-Enriched Gas and Compression Thereof for High PressureMobile Storage Utilization, the entire disclosures of which are fullyincorporated by reference herein.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to an apparatus and process for conservingenriched oxygen which is subsequently collected under high pressure in aportable container for ambulatory patient use and to permit facilepatient mobility. A multi-stage radial compressor is utilized topressurize the desired gas. The enriched oxygen is fed at a reducedpressure from a product storage tank to a patient, and at the storagetank pressure to generally a buffer tank and subsequently to a radialcompressor.

Heretofore, oxygen concentrators have been utilized to supply patientswith a gas having a high oxygen concentration for extended periods oftime. Oxygen concentrators typically produce a breathable gas containingfrom about 80 percent to about 96 percent oxygen from atmospheric airand thus have been widely utilized in the home health care field.

U.S. Pat. No. 4,627,860, to Rowland, relates to a microprocessor andcooperating means for monitoring or sensing functions and performance ofvarious components of the concentrator. A test apparatus having meansfor selecting any of the functions monitored by the microprocessor isconnected to the concentrator and displays the selected monitoredfunctions for diagnosing performance levels and component problems orfailures.

U.S. Pat. No. 5,071,453, to Hradek et al. relates to an oxygenconcentrator which is intended for aircraft use. A booster compressor isused to increase the pressure of the product gas from the concentratorin order to increase the amount of the gas which can be stored in aplenum. The booster includes two moving pistons which are rigidly linkedtogether and a series of check valves which control the flow of gasesthrough the compressor. One of the pistons is driven by air from therotary valve in the concentrator, and the other piston compresses theproduct gas for delivery to the plenum. A small sample of concentratorproduct gas is monitored by an oxygen sensor for oxygen concentration.Once the oxygen concentration has reached an acceptable level, thebooster compressor fills the plenum with product gas. Thereafter, if theoxygen concentration of product gas delivered to the crew from theconcentrator falls below the concentration which is required at aparticular altitude, the product gas stored in the plenum is deliveredto the crew. The oxygen sensor monitors the concentrator output productgas to the breathing regulator when the stored plenum gas is not beingused.

U.S. Pat. No. 5,354,361, to Coffield, relates to a pressure-swingadsorber system including a pneumatically driven booster compressor toincrease the pressure of the output product gas. A pair of inlet valvescontrols feed air flow to the sieve beds and the drive cylinder of thebooster compressor and are cycled so that one valve opens to pressurizeone sieve bed before the other valve closes to allow the other sieve bedto vent to atmosphere. During the time that both valves are open, thepressure in the two sieve beds and on opposite sides of the drivecylinder equalize and a portion of the gas in the pressurized sieve bedand drive cylinder side is captured rather than being vented to ambient.System efficiency is increased by selecting whether captured gas fromthe last pressurized sieve bed or drive cylinder side reaches the nextto be pressurized sieve bed first.

U.S. Pat. No. 5,858,062, assigned to Litton Systems, Inc., relates to anapparatus for providing oxygen-enriched air at a first pressure and at asecond pressure, the second pressure being greater than the firstpressure. The apparatus comprises, in combination, a pressure swingadsorption system and a pressure intensifier. The pressure swingadsorption system for enriching the oxygen content of air has a pressureof at least the first pressure. The pressure swing adsorption system isadapted to provide oxygen-enriched air to a first outlet at the firstpressure and to provide oxygen-enriched air to a pressure intensifier atthe first pressure. The pressure intensifier pressurizes theoxygen-enriched air and provides the oxygen-enriched air to a secondoutlet at the second pressure.

SUMMARY OF INVENTION

It is an aspect of the present invention to provide a method andapparatus for storing high-pressure, high-purity oxygen in a pressurevessel for use in the home health care or related fields as forambulatory patients, persons confined to wheelchairs, and those who arebedridden.

In accordance with the invention there is provided a method andapparatus for producing from air an oxygen-enriched gas and initiallystoring the same in a concentrator product tank. At least a portion ofthe oxygen-enriched gas is fed by different methods as to an optionalbut desired compressor buffer tank where it is stored. After reaching apredetermined pressure, the gas is fed to a compressor where it iscompressed to a high pressure and stored in a mobile or portablehigh-pressure container. A patient can thus have increased mobilitythrough use of the portable, one or more high-pressure oxygencontainers, which can be filled in one's own home.

It is a further aspect of the invention to provide circuitry to assureprioritization of the flow rate and concentration of the enriched gas toa patient. The excess gas, when available, is simultaneously deliveredto an independent, multi-stage compressor.

In accordance with another aspect of the invention there is provided ahome health care oxygen concentrator for physically separating moleculesof oxygen from air with oxygen in a subsequent operation being fed to ahigh-pressure vessel. The concentrator comprises one or more molecularsieve beds containing a physical separation material, a first (i.e.,feed stock) compressor to provide a feed source of compressed air,control means which regulate the product gas flow through the beds to aconcentrator product tank, a second enriched-gas storage tank (e.g., abuffer tank), and a second compressor, e.g., multi-stage, which is notoperated by the first compressor but operates independently thereof andenables the oxygen-enriched gas to be compressed and fed to ahigh-pressure vessel or container.

In a further embodiment, a radial compressor can be utilized to compressoxygen from an optional but desired buffer tank connected to an oxygensource. The radial compressor has pistons radially arranged around acentral drive shaft and compresses the oxygen to a high pressure andstores the same in a compact storage cylinder. This design is morecompact and less bulky than typical linear designed compressors, andallows the compressor to be housed in a relatively small unit which isthus more easily transportable. An oxygen sensor determines whether arequired minimum oxygen concentration is being supplied to a patient andif not, terminates the flow of compressed oxygen to the cylinder, whilemaintaining the flow to the patient.

Still another embodiment relates to an oxygen storage tank whichoperatively feeds oxygen-enriched gas to a patient and which alsoindependently and operatively feeds enriched oxygen at a different andgenerally greater pressure to a buffer tank where subsequently it iscompressed by a compressor, independent of an initial compressor forfeeding air to the molecular sieves.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an oxygen concentrator for separatingoxygen from a gaseous mixture such as air;

FIG. 2 is a block diagram of an apparatus and process in accordance withthe present invention for compressing oxygen-enriched air and feeding itto a portable container;

FIG. 3 is a block diagram of the apparatus and process of the presentinvention for feeding a portion of enriched gas at a controlled rate toa patient and another portion of the enriched gas to a compressor forhigh-pressure storage in a portable container;

FIG. 4 is a block diagram of the apparatus and process of anotherembodiment of the present invention for feeding a portion of enrichedgas at a controlled rate to a patient and another portion of theenriched gas to a compressor for high-pressure storage in a portablecontainer;

FIG. 5 is a schematic showing one portion of a control circuit foroperating a multiple-stage compressor of the present invention;

FIG. 6 is a schematic of the remaining portion of the control circuit ofFIG. 5 for operating a multiple-stage compressor of the presentinvention;

FIG. 7 is a side elevational view of the compression apparatus of thepresent invention;

FIG. 8 is a top plan view of the compression apparatus of the presentinvention;

FIG. 9 is a side elevational view of the upper portion of the two-partpiston assembly of the present invention;

FIG. 10 is a side elevational view of the bottom portion of the two-partpiston assembly of the present invention;

FIG. 11 is a top plan view of a radial compressor of the presentinvention;

FIG. 12 is a perspective view of the radial compressor of FIG. 11showing inlet and outlet connections of the compression cylinders;

FIG. 13 is a perspective view of the portable high pressure oxygenconserving device of the present invention;

FIG. 14 is a mechanical and quasi-electrical schematic of the radialcompressor and the flow system of the present invention;

FIG. 15 is a block diagram of the electrical circuitry of the inventionincluding an oxygen concentration test mode aspect;

FIG. 16 is a block diagram of the apparatus and process of the preferredembodiment showing the general flow at different pressures ofoxygen-enriched gas from an oxygen or product storage tank to a patientas well as to eventually a compressor for compression and delivery to ahigh pressure, portable, storage cylinder;

FIG. 17 is a detailed view of the embodiment shown in FIG. 16, includingthe buffer tank, compressor and high pressure cylinder; and

FIG. 18 is a detailed view of the embodiment shown in FIG. 16, includinga controller apparatus.

DETAILED DESCRIPTION

While a preferred embodiment of the invention is described hereinbelow,it is to be understood that the various aspects and parameters of thepresent invention can vary and be different such as the pressure andpurity of the oxygen-enriched gas exiting from a concentration producttank, the pressure at which the enriched gas is fed to the patient andits flow rate, the pressure maintained in a buffer tank, the pressure atwhich the compressor initially draws enriched gas from the buffer tank,the buffer tank pressure at which the compressor shuts off, and thelike. Moreover, while reference is made to a particular oxygenconcentrator as set forth immediately below, generally any type ofoxygen concentrator can be utilized which yields a source of enrichedair containing anywhere from about 50 percent oxygen up to about 99percent by volume.

With reference to FIG. 1, the apparatus includes one or more, andpreferably two beds 10 and 12 which contain a physical separation mediumor material. The separation material selectively adsorbs one or moreadsorbable components as from air and passes one or more nonadsorbablecomponents of such a gaseous mixture. The physical separation materialcan be a molecular sieve with pores of uniform size and essentially thesame molecular dimensions. These pores selectively adsorb molecules inaccordance with molecular shape, polarity, degree of saturation, and thelike. In the preferred embodiment, the physical separation medium is analuminasilicate composition with 4 to 5 A (Angstrom) pores. Morespecifically, the molecular sieve is a sodium or calcium form ofaluminasilicate, such as type 5A zeolite. Alternately, thealuminasilicate may have a higher silicon-to-aluminum ratio, largerpores, and an affinity for polar molecules, e.g., type 13x zeolite. Thezeolite adsorbs nitrogen, carbon monoxide, carbon dioxide, water vapor,and other significant components of air.

A cross-over valving means 20, which preferably includes a four-wayvalve 21, selectively and cyclically connects the inlet end of two beds,one at a time, during a production phase with a source of the gasmixture, e.g., air under pressure supplied from a first compressor 22(i.e., the feed compressor), while the other bed is vented to atmosphereduring a purge phase. Specific to the preferred embodiment, thecross-over valving means selectively connects one of the beds in fluidcommunication with an air pump or compressor 22 which supplies air fromabout 15 to about 21 psi. As used herein, “fluid communication” refersto means allowing flow of the appropriate gases. Of course, vacuum canalso be used during the purge phase with the present invention toenhance evacuation. Compressor 22, which receives air from inlet 23, isconnected to a first drive motor 25, in the preferred embodiment about a¼-horsepower electric motor. A solenoid (not shown) or other cross-overvalve actuating means selectively causes the cross-over valving means tomove alternately between first and second positions. In the firstposition, the first bed 10 is connected with compressor 22 to causenitrogen adsorption and oxygen enrichment in the product gas, and thesecond bed 12 is vented to atmosphere to allow evacuation. In the secondposition, the first bed is vented to atmosphere to allow evacuation andthe second bed is connected with the air compressor to cause nitrogenadsorption. The invention is described with specific reference to apressure-swing control. However, it is equally applicable to othermethods of sequencing the gas flow through the sieve beds such as atiming-based system.

The composition of the gas in the voids of the zeolite varies fromsubstantially pure primary-product gas at the outlet end, to the ambientgaseous mixture composition at the inlet end. As the gas mixture isintroduced through a bed inlet to an adsorbed, gas-free or regeneratedbed, an adsorption zone of finite, relatively large size is formed. Thisadsorption zone is a region of the bed in which the full capacity of theadsorbent to hold the adsorbable components has not been reached. Thisadsorption zone moves from the bed inlet toward a bed outlet with avelocity significantly less than the superficial gas velocity in thebed. When the adsorption zone reaches the outlet end of the bed,adsorbable components begin to flow through the bed outlet into thenonadsorbable primary product stream. This time is hereinafter referredto as the “breakthrough.” For a given gaseous composition, thebreakthrough is defined by the size and configuration of the bedcontainer as well as the packing configuration of the molecular sieveand the flow rate and bed gas pressure. The configuration of the bed isgenerally cylindrical and the output volume rate can vary from about 0.1to 6 liters per minute. The breakthrough is the time required for thediffusion reaction as the nitrogen saturates and is weakly bonded to thesieve bed. When breakthrough occurs, primary product-enriched bed gas inthe zeolite voids varies from a higher primary product gas concentrationat the bed outlet to a lower concentration at the bed inlet. In thepreferred embodiment, the primary product-enriched bed gas is about 80percent primary product at breakthrough. While adsorption is occurringin one bed, the adsorbable components adsorbed by the separation mediumof the other bed are purged from the other bed because of the drop inpressure due to atmospheric venting and because of exposure torelatively pure product gas from the first tank.

The first bed 10 is connected with a reservoir or product tank 30 by wayof a first check valve 32 or other unidirectional valving means. Thefirst check valve 32 permits the primary product gas from the first bed10 to flow into the reservoir or product tank 30 via line 46 when theproduct gas pressure in the first bed 10 exceeds the pressure of productgas in the reservoir or product tank 30. The first check valve prohibitsthe product gas from flowing from the reservoir or product tank 30 whenthe pressure in the first bed 10 is lower than the reservoir or producttank. More specific to the preferred embodiment, the check valve imposesa 1.5 psi bias such that flow is only permitted when the pressure in thefirst bed exceeds the pressure in the reservoir or product tank by 1.5psi. The second bed 12 is connected with the reservoir or product tank30 by way of a second check valve 34 or other unidirectional valvingmeans. The second check valve 34 again provides for unidirectional flowof the primary product gas from the second bed 12 to the reservoir orproduct tank 30.

A pressure equalization flow path 40 extends between outlets of thefirst and second beds. A concentration equalization valve 42 is eitheropen or closed to selectively permit or prevent gas flow through theflow path between the first and second beds. A control means 50cyclically causes the cross-over valve actuating means (i.e., twosolenoids) and the concentration equalization valve 42 to be operated.The control means periodically and cyclically enables a concentrationequalization valve actuator which is also a solenoid.

Oxygen sensor 43 registers the oxygen concentration of the product gasand can be located in the product tank 30. The sensor 43 communicates asensed value to the microprocessor (i.e., control means). Similarly, apressure sensor 45 registers the pressure in the product tank andcommunicates the same to the microprocessor.

The control means causes the cross-over valving means 20 to alternatebetween its first and second positions for the appropriate period duringeach cycle segment. A cycle segment can be either the product gasgeneration cycle or the purge cycle. The cycle duration is selected suchthat each bed is connected with the source of air for a period of timewhich is equal to or less than the breakthrough time. The mechanismwhich triggers the cross-over valving can be based on the pressure, suchas a pressure set point or set point range, in the bleed line from theproduct tank as is used in a pressure-based control cycle, or it can bebased strictly on a residence time from the product-producing bed, suchas in a timing cycle-based control cycle. In accordance with anotherembodiment of the invention, the control cycle can utilize variablepressure in order to achieve a residence time within a defined rangebased upon a projected breakthrough time. In the preferred embodiment,the beds are 3.5 inches in diameter, 15 inches in length, and eachcontains 6.5 pounds of 5A zeolite.

The gas mixture is supplied at up to 21 psi of pressure to the firstbed. Concurrently, the second bed (i.e., a “used” bed) is vented toatmosphere to cause purging of the nitrogen-enriched molecular sieves.Before the breakthrough time, the concentration equalization valve isopened allowing primary product-enriched gas from the first bed to flowinto the evacuated second bed. During the concentration equalizationperiod, one bed is evacuated and the other has just reached the pressureset point which drives flow between the beds. The flow is of high oxygencontent so that the first product to pass into the product tank via line46 is essentially product gas produced by the oxygen beds. The secondbed pressure is product-enriched gas to purge the sieve bed. Before theprimary product-enriched gas from the first bed is evacuated through thesecond bed, the cross-over valving means 20 is actuated to reverse itsposition. Actuating the cross-over valving means discontinues supplyingof the gaseous mixture to the first bed and commences evacuating it andconcurrently discontinues evacuating the second bed and commencessupplying it with the gaseous mixture.

Subsequent to the actuation of the cross-over valving means, theconcentration equalization valve 42 remains open to continue allowing apurge supply of product-enriched gas to flow into the second bed. Thisequalizes the concentration of gas which is supplied to the product tanksince the cycling is sequenced so that the product gas proceeds from thebreakthrough zone to flow into the product tank. Subsequently, theconcentration equalization valve closes and terminates the flow ofprimary-product gas between the beds. In the second segment of thecycle, the pressure in the second bed increases approaching the gasmixture source pressure. Concurrently, the pressure in the first beddecreases approaching atmospheric pressure. Before the secondary productmolecules have traversed the second bed, the concentration equalizationvalve 42 is opened allowing the primary product-enriched gas in thezeolite voids of the second bed to flow to the first bed. While theprimary product-enriched gas is flowing to the first bed, the cross-overvalving means is actuated. Actuating the cross-over valving meansdiscontinues the evacuation of the first bed and commences supplying thegaseous mixture and concurrently discontinues supplying the gaseousmixture to the second bed and commences evacuating it. Subsequent toactuating the cross-over valving means, the concentration equalizationvalve is closed terminating the pressure equalizing flow of the primaryproduct-enriched gas between the beds. The steps are cyclically repeatedto provide continuing fractionating of the primary product gas from themixture.

Referring again to FIG. 1, in a preferred embodiment the reservoir orproduct tank 30 maintains a reservoir of oxygen at a minimum pressure ofabout 14 psi. The oxygen-enriched gas contains from about 50 to about 99percent, desirably from about 70 to about 98 percent, and preferablyfrom about 84 to about 96 percent by volume of oxygen. In accordancewith conventional procedures, product tank 30 can be connected to apressure regulator (not shown) for controlling the pressure of theoxygen to a patient. Typically a pressure of 5 psi is utilized. A flowmeter (also not shown in FIG. 1) can be utilized to limit the flow rateto the patient such as from 0.1 to about 6 liters per minute with a flowrate of about 3 liters per minute often being utilized. If desired, ahumidifier (not shown) can add moisture to the oxygen-enriched gas. Thegas is delivered to the patient via tubing and breathing apparatus whichcan be inserted into the patient's nostrils.

In accordance with other concepts of the present invention,oxygen-enriched gas from an oxygen concentrator such as that describedhereinabove can be fed in any variety of methods to a compressor whereit is compressed to very high pressure and stored in a portable ormobile container such as a gas cylinder.

In the embodiment of FIG. 2, all of the oxygen-enriched gas is fed to acompressor. A concentrator (not shown but such as described hereinabove)has an oxygen-enriched product tank 30 wherein the pressure can vary asfrom about 14 to about 21 psi. The oxygen-enriched gas therein is fedvia line 201 to a flow meter 210 at the pressure of the concentratortank, that is from about 14 to about 21 psi. Flow meter 210 controls theflow rate of the oxygen-enriched gas which is fed via line 211 to buffertank 220 wherein the gas pressure therein can also range from about 14to about 21 psi. Via line 221, the predominantly oxygen gas is fed tocompressor 100. Compressor 100, in a manner described below, compressesthe oxygen-enriched gas to a pressure of about 2,250 psi and stores itwithin a mobile or portable cylinder 500. Depending upon the withdrawalrate of the oxygen-enriched gas by the compressor, the feed pressurethereto can range from 21 psi down to a predetermined cut-off pressuresuch as about 5 or 7 psi whereupon the compressor is automatically shutoff by a pressure sensor switch.

FIGS. 3 and 4 relate to embodiments wherein oxygen-enriched air fromproduct tank 30 of the oxygenator is fed by various methods desirably toa buffer tank of the compressor but prioritized as with regard to oxygenconcentration and/or a sufficient pressure. For example, the feed rateto a patient can vary from between 0.1 and 6 liters per minute at apressure of a predetermined value such as 5 psi with the remainingoxygen-enriched gas generally being fed at a different pressure to thebuffer tank. The buffer tank can generally contain a broad range ofpressure therein such as, for example, between 14 and 21 psi. However,as noted with regard to FIG. 2, depending upon the withdrawal rate ofthe gas in the buffer tank by the compressor, the pressure thereof candrop down to a predetermined cut-off pressure, such as 7 psi, which ishigher than the pressure of the gas being fed to the patient to ensurean adequate flow of the oxygen-enriched gas to the patient.

Referring to the embodiment of FIG. 3, a 5-psi regulator 210 emitsoxygen-enriched gas from product tank 30 into flow line 220 and feedsthe same to flow meter 230 which subsequently emits the oxygen-enrichedgas to the patient at a predetermined flow rate of from 0.1 to 6 litersper minute. Optionally, the flow meter can be closed so that all theenriched oxygen is directed to the compressor. Gas not directed to thepatient is carried via line 240 to two-way valve 250. A very smallportion of the gas in line 220 is directed through line 260 throughrestrictor 262 into oxygen sensor 265 which detects whether or not theconcentration of the oxygen is of a predetermined value such as is atleast 84 percent. When the oxygen sensor detects a concentration at orabove the predetermined level, two-way valve 250 is open and permits theoxygen-enriched gas to flow through line 270 into buffer tank 200wherein the pressure is essentially the same as the oxygen product tankpressure. However, should the oxygen sensor not detect a suitable oxygenconcentration, two-way valve 250 is closed so that the oxygenconcentrator can build up a sufficient oxygen concentration. Thisarrangement prioritizes the flow of oxygen-enriched gas so that thepatient is assured of receiving a gas having a minimum oxygenconcentration therein. Buffer tank 200 can have a regulator 280 thereongenerally set at 12 psi to admit the oxygen-enriched gas to thecompressor when needed. Alternatively, the pressure regulator can be setat anywhere from about 13 to about 21 psi. Restrictor 290 controls theflow rate of gas from the buffer tank to the compressor. Should thecompressor drop the pressure in the buffer tank to below a predeterminedvalue, a pressure sensor (not shown) will automatically cut off the flowof gas at a pressure above the pressure of the gas being fed to thepatient. This prioritization assures that the patient receives prioritywith regard to oxygen-enriched gas.

The embodiment of FIG. 4 emits the oxygen-enriched gas through a 14 toabout an 18-psi regulator 300 into flow line 305 having flow raterestrictor 307. The flow is then split with a portion via line 310 goingthrough 5-psi regulator 320 and into flow meter 330 which then directsthe gas to the patient at a desired flow rate of generally from 0.1 to 6liters per minute, although optionally the flow meter can be closed. Theremaining portion of the gas is directed via line 340 to two-way valve350. A small portion of the gas going to the patient is diverted throughline 365 through flow restrictor 367 to oxygen sensor 360. As in FIG. 3,the oxygen sensor is set at a predetermined value such as aconcentration of 84 percent so that when the level is not achieved,two-way valve 350 is closed through electrical line 355. This aspectallows the amount of oxygen in the concentrator tank to be increased bythe oxygenator unit. The same prioritizes the concentration of oxygen toensure that the patient receives an amount of oxygen of at least theminimum predetermined value. When the oxygen concentration issufficient, the gas flows through two-way valve 350 into line 370 andinto buffer tank 200 where it is stored generally at a pressure of about14 to 18 psi. A relief valve 385 which can be set at any desired valuesuch as about 14 psi ensures that gas under sufficient pressure is beingadmitted to the buffer tank. The oxygen-enriched gas is admitted to thecompressor via line 380. Should the compressor withdraw gas faster thanit is being received by the buffer tank, the pressure therein will drop.A pressure sensor switch (not shown) can be set to a predetermined value(e.g., about 7 psi) to ensure or prioritize that a sufficient amount orflow of gas is being fed to the patient. The predetermined shut-offpressure of the compressor is always above the pressure of the gas beingfed to the patient. The embodiment of FIG. 4 is preferred.

While the above description, as exemplified by FIGS. 2, 3, and 4,generally constitutes a preferred embodiment of the present invention,it is to be understood that the same can be modified. For example,oxygen product tank 30 need not be utilized. Instead, theoxygen-enriched air from an oxygen concentrator, such as shown in FIG.1, can be fed to the buffer tank via the shown and described flow linesof the various embodiments such as set forth in FIGS. 2, 3, and 4.Accordingly, the oxygen-enriched air will be separated with onecomponent directed to the patient and the other component being directedto the buffer tank. Prioritization of the oxygen-enriched gas to thepatient either by a minimum oxygen concentration or a sufficientpressure in the buffer tank is still generally utilized. Alternatively,an enriched oxygen product tank 30 can be utilized and the buffer tankcan optionally be eliminated. In other words, enriched oxygen from theproduct tank can be fed via one component to the patient and to a secondcomponent via the flow line shown to the compressor. In this situation,prioritization of the desired flow and oxygen concentration to thepatient is maintained as described hereinabove with regard to either thelevel of oxygen concentration or an adequate pressure being admitted tothe compressor.

Referring now to the compressor assembly 100 as shown in FIGS. 7 and 8,it generally utilizes an AC electric-drive motor 105 which can rotate atany desired speed, e.g., 1,700 rpm. Motor 105 can contain a fan (notshown) either within the motor housing or immediately adjacent theretoto draw air through the motor to cool the same. Power is conveyed fromthe motor through shaft 106 to drive wheel 107. Desirably the drivewheel has a plurality of grooves therein to receive a V-belt such asmain drive belt 109. Such belts are generally reinforced with fiber andhave a very long life. Main drive belt 109 is connected to main gear 110which contains a plurality of grooves 113 therein. The number ofperipheral grooves 113, as well as the size and location thereof,coincides with the grooves of drive wheel 107 and matingly engage aplurality of projections located on main drive belt 109. Extending frommain gear 110 is an offset hub gear 114 which has a much smallerdiameter than main gear 110. Hub gear 114 also has grooves 115 thereonto receive a secondary drive V-belt 122. A second or secondary largegear 116 has grooves on the periphery thereof which matingly engage thesecondary drive V-belt 122. Offset hub 114 through the secondary V-drivebelt 122 contacts and serves to drive secondary gear 116 which in turnis connected to crankshaft 130.

Through the utilization of the two large gears 110 and 116, adouble-reduction is obtained such that the rotational speed ofcrankshaft 130 is a desirably low speed such as approximately 50 rpm.Both drive belts 109 and 122 desirably have a spring-loaded idler arm125 and 127, respectively, which applies a small amount of tension. Theactual pull tension of the first belt can be about 20 pounds, whereasthe tension on the second belt can be about 100 pounds.

The multi-stage compressor of the present invention can have any numberof pistons, but in the present embodiment has three. As shown in FIG. 8,two of the pistons, i.e., the first and third pistons, are located onthe same crankshaft lobe, whereas the second piston is located on adifferent lobe offset 180° from the first and third pistons. The reasonfor this is that pistons one and three will be drawing in air when thesecond piston is being compressed and vice versa. Although not shown, acrankshaft can be utilized which contains three lobes thereon, eachoffset from one another by approximately 110 degrees to 130 degrees,e.g., about 120 degrees, so as to minimize the torque resistance appliedto the motor during the compression stroke.

The compressor of the present invention has three pistons, i.e., piston#1 (131), piston #2 (133), and piston #3 (135). Each piston is containedwithin a separate cylinder and thus piston #1 is contained within thefirst cylinder (132), the second piston is contained the second cylinder(134), and the third piston is contained within the third cylinder(136). While the diameter of the head 140 of the first piston isapproximately equal to the diameter of the base portion of the piston asshown in FIGS. 8 and 9, the diameter of the head of piston #2 (133) issmaller than that of piston #1, and the diameter of the head of piston#3 (135) is smaller than the diameter of piston #2 (133). However, thebase of each piston 131B, 133B, and 135B is of the same size for reasonsset forth hereinbelow. In order to permit pistons #2 and #3 to operateproperly, each contains an annular sleeve 134S and 136S on the inside ofthe cylinder wall the internal diameter of which is approximately equalto the external diameter of piston heads #2 and #3 respectively.

Regardless of the size of the piston head, it has two rings as generallyindicated in FIG. 9. Inasmuch as the rings of all three piston heads aregenerally the same, only the first piston is shown in FIG. 9. The pistonhead has two annular grooves or recesses therein, that is top pistonannulus 141 and bottom annulus 144. The top annulus contains a U-shapedseal therein generally made out of a Teflon® alloy or other low-frictionmaterial. The seal contains a coil tension spring 143 therein whichforces the seal radially outward against the cylinder wall to preventcompressed air from leaking through the piston head between the pistonand the cylinder wall. To also ensure the maintenance of a good seal,seal 142 is U-shaped so that upon the build-up of pressure in thecylinder head, the compressed gas will communicate and enter into theseal and force the outer edge thereof radially outward against thecylinder wall. Piston head bottom annulus 144 contains a flat orvertical glide ring 145 which extends around the annulus and is alsoradially forced outwardly by a coil tension spring 146 located therein.The bottom glide ring 145 can be made out of a Teflon® alloy and servesas a piston glide ring.

Connecting rod 148 connects the piston head to piston base 150. Thepiston bases of all three pistons are the same diameter and accordinglyengage a mating cylinder of essentially the same diameter. The pistonbase contains an upper base annulus 151 and a lower base annulus 155,both of which have a glide ring therein similar to if not identical toglide ring 145 of piston head annulus 144. Thus, upper base annulus 151has a glide ring 152 therein which is forced radially outward by coilspring 153. Similarly, lower base annulus 155 has a glide ring 156therein which is radially forced out by coil-spring 157. Although threeglide rings have been shown and described as being identical, they canbe different and use different material, and the like. Piston base 150contains bore 158 which extends laterally therethrough. Bore 158receives wrist pin 159. The wrist pin and coil spring both serve tomaintain glide ring 156 in a radially outward position so as to bearagainst the cylinder wall.

The two-part piston assembly of the present invention contains bottomconnecting rod 160 as shown in FIG. 10. The connecting rod contains atop bore 161 through which wrist pin 159 extends. Bottom bore 163 of theconnecting rod extends about and matingly engages an appropriate portionof the crankshaft. In order to permit rotation of connecting rod 160about the crankshaft 130, sealed portion 164 of the connecting rodcontains bearings therein.

The net result of the two-part piston ring assembly of the presentinvention is that bearing 164 of connecting rod 160 can freely rotatewith the crankshaft in a rotary or circular motion whereas top bore 161moves in only a linear or reciprocal motion allowing piston rod 148 withthe piston head and base thereon to move only in a linear reciprocatingdirection. The same thus prevents lateral forces from being applied tothe cylinder wall which often results in wear and can create anoval-shaped cylinder wall. The two-part piston ring assembly of thepresent invention thus promotes long life of the piston and cylinderwall.

Although each piston serves to compress the gas admitted therein to ahigher pressure, a desirable aspect of the present invention, as notedabove, is that each subsequent piston head has a smaller area. Forexample, piston #1 (131) can have a diameter of approximately 1¾ inches,whereas piston #2 has a diameter of approximately 1¼ inches, and piston#3 can have a diameter of approximately ½ inch, which can be thediameter of essentially piston rod 148. Desirably, the increase inpressure from each stage or piston is proportional to the others. Thecompression ratio of each piston can vary, but generally is the same.Although compression ratios of up to 10 can be utilized, the desirablepressure range is from approximately 6 to about 8.

Inasmuch as heat is built-up during compression of the oxygen-enrichedgas, the flow lines between the pistons can be extended so that they arelong enough to permit the heat of compression to be absorbed by ambientair and thus cool the enriched pressurized gas therein. As shown in FIG.8, cooling line 182 from the first piston to the second piston can be inthe form of an undulating path or the like and the same is true withregard to cooling line 184 between the second and third pistons.

The operation of the compressor portion of the apparatus is as follows.Electric motor 105 which operates independently of the compressorfeeding air to the molecular sieves in the oxygen concentrator portionof the apparatus, through drive belts 109 and 122, rotates crankshaft130 thereby causing piston #1, #2, and #3 (131, 133, 135) to reciprocateand compress air in their respective chambers. More specifically,enriched oxygen gas from the compressor buffer tank is fed to the firstpiston. Piston 131 contains an inlet check valve 172, which permits airto enter the cylinder head space above the piston, and outlet checkvalve 173, which permits the compressed gas to exit from the firstpiston. The check valves permit flow of the gas in one direction so thatonce the gas is admitted to the first piston, during the compressionstroke thereof it cannot be forced back out to the buffer tank.Similarly, once forced out of the first piston, outlet check valve 173prevents the gas from being sucked in during the intake stroke of thefirst piston. In a similar manner, second piston 133 has an inlet checkvalve 175 which permits the compressed air from piston #1 to be drawninto the head space above piston 133, but prevents it from being forcedback into the first piston. Outlet check valve 176 prevents the gascompressing the second piston from being drawn back into the piston onceit has been expelled therefrom. In a similar manner, the gas which hasbeen further compressed in piston #2 is fed into piston #3 (135) throughinlet check valve 178 where it is further compressed. The compressed gasis then fed through outlet check valve 179 into enriched oxygen gasstorage cylinder 500. Outlet check valve 179 thus prevents the highlycompressed stored gas in the cylinder from being admitted back into thethird piston.

During the operation of the compressor, the gas in portable cylinder 500which is initially at ambient pressure, is gradually built up to desiredpressure. One such suitable pressure is approximately 2,250 psi. Ofcourse, different cylinders can accept either higher or lower gaspressures and readily maintain the same. Rupture disk 180 is a safetyfeature designed to rupture at a pressure in excess of the desiredstorage pressure of the gas cylinder. Thus, in the present embodiment,such a pressure can be approximately 2,800 psi. Although not shown,rupture disks can also be provided in the flow lines from the exit ofthe first and second cylinders to prevent undue build-up in these lines.A pressure regulator 181 serves to emit the oxygen-enriched gas at apressure of about 5 psi to a patient via a flow meter (not shown) at anydesired rate, such as from about 0.1 to about 6 liters per minute.

As previously noted, the buffer tank contains oxygen-enriched gas at apressure of generally from about 7 or 14 psi to about 21 psi. Thecompressor is designed to commence compression generally when thepressure in the tank is generally at a maximum until it drops to apredetermined pressure, e.g., 7 or 8 psi. In general, the pressure iselectrically controlled by various switches, sensors, relays and thelike. Briefly, a master ON/OFF switch emits power to compressor motor105 which in turn causes the crankshaft to rotate and compress air. Twopressure-sensitive switches exist: a low pressure sensor which detectspressure below a predetermined value, e.g., 7 to 12 psi, and a highpressure sensor which detects pressure above 2,250 psi. When the lowpressure sensor detects pressure below the predetermined level, it willturn off motor 105 through a relay switch. This allows oxygen inflowfrom the concentrator to be built-up in the buffer tank to a desiredpressure. The low pressure sensor is a-solid-state relay. Should therelay fail, it will fail closed and allow the motor to continue to run.Accordingly, this relay switch is connected in series with the highpressure sensor mechanical relay switch which will shut the motor offwhen the pressure in the cylinder reaches approximately 2,250 psi.

FIGS. 5 and 6 show the electrical circuitry of the compressor. Power isfed to the compressor initially through the resettable breaker 600 andthen to power switch 610. When the power switch is pushed to the “ON”position, power passes to the motor start switch 620, the start relaycommon contacts 630, and also lights the power indicator 640. When startswitch is depressed, the start relay coil is energized which causes bothswitches of the relay to close.

One of these closed switches passes the power to high pressure switch650 which is normally closed when the output pressure of the compressoris under 2,250 psi. The output of the high pressure switch is fed backto the start relay coil to keep the coil energized without the startswitch being depressed, but will cut power to the coil when highpressure is reached. (This occurs when a tank has been filled.) Theoutput of the high pressure switch is also connected to the common oflow pressure switch 660. While the input pressure from the concentratoris above the predetermined value, e.g., 7 psi, the low pressure switchis closed and the normally closed contact has power. This power signalis fed to the drive contact of the solid-state relay which, in turn,allows the solid-state output to be “turned on.” The output of thehigh-pressure switch is also connected to the run indicator 670 whichthen lights up.

The second closed switch of the start relay is connected to the “input”of the solid-state relay. When the solid-state relay is turned on by thesignal from the low pressure switch, power is passed to motor 105 andits start capacitors through the solid-state output. A common line isconnected to the other side of the motor to complete the circuit. Anhour meter 690 is wired in parallel to the motor to monitor motor runtime.

When the above occurs, the motor beings to run and remains running untilone of two conditions occur. The first condition would be the inputpressure to the compressor falls below a predetermined value, e.g., 7psi. This will cause low pressure switch 660 to open and solid-staterelay 695 to turn off, which in turn shuts off motor 105. If the inputpressure to the compressor rises above a desired predetermined pressure,low pressure switch 660 will close and once again turn on thesolid-state relay and start the motor. This is a normal occurrence thatis dependent upon concentrator efficiency and may be repetitive.

The second condition that will shut off the motor occurs when an oxygentank has been filled. The output pressure will rise above 2,250 psi andtherefore cause high pressure switch 650 to open. This cuts the power tothe start relay coil which causes both switches to open and cuts thepower to both the input of the high pressure switch and the input to thesolid-state relay thereby shutting off the motor. To start the motorafter this condition is reached requires start switch 620 to bedepressed. If greater than 2,250 psi remains, the high pressure switchwill remain open and no signal will be fed back to the start relay coilto keep it energized therefore causing the motor to remain off. Whilethe high pressure switch is open, run indicator 670 remains off.

Any direct shorts between power and common or any condition that drawsmore than 8 amps of current will cause resettable breaker 600 to popopen.

As apparent from the above, the operation of compressor 100 iscompletely independent of the oxygen concentrator as well as utilizationof gas compressed thereby as a power or energy source for thecompressor. In other words, the pressure accumulated in the oxygenconcentrator is not utilized to drive or operate a pressure intensifier.

A distinct advantage of the apparatus and method for forming oxygenenriched gas and compression thereof according to the present inventionis the creation of a mobile or portable source of gas containing highpurity oxygen. Patients who require oxygen-enriched gas, as from about80 to about 98 percent, are no longer confined to the vicinity of anoxygen concentrator as for example a bed, home, hospital, or awheelchair. Rather, the patient can carry the mobile gas cylinder in anyconvenient manner, such as in a backpack, and thus can take trips viawheelchair, an automobile, and even planes and trains. Depending uponthe pressure and size of the storage cylinder, the oxygen supply can beanywhere from about 2 to about 24 hours or even longer.

A further embodiment of the present invention relates to anelectromechanical oxygen distribution device or system as for use in ahome to supply a patient with concentrated oxygen and also toconcurrently supply pressurized and concentrated oxygen to a storagecylinder as for a patient's personal ambulatory use. The device isdesigned to be utilized in association with an oxygen source capable ofsupplying oxygen at a preferred concentration of at least 85 percent or90 percent by volume at various pressures such as generally from about 2to about 20 psig, and desirably from about 2.5 or about 4 to about 10psig. Sources of concentrated oxygen include an oxygen concentrator asset forth herein above, or, conventional or commercially availableoxygen concentrators, such as for example, but not limited to,Mallinckrodt-Aeris 590; Russ ProductsMillienum; Sunrise; and the like.Such concentrators can have various oxygen concentration outputs,pressures, and a desirable flow rates such as at least about 3, 5 or 6liters per minute.

The oxygen distribution system or device 800 has housing 810 as well asoxygen test mode inlet 815, oxygen normal operation inlet 820 forreceiving oxygen from a concentrated oxygen source, oxygen outlet 825for feeding oxygen to a patient, oxygen flow meter 830 for regulatingthe flow of oxygen to a patient, pressure gauge 835, power switch 840for turning the compressor unit or device on and off, and fill connector845 for connecting the compressed gas to gas storage cylinder 1000.

Considering the radial compressor, as seen in FIGS. 11 and 12 the radialcompressor generally utilizes an AC electric drive motor 905 which canrotate at any desired speed, such as generally from about 500 or 1,000to about 3,600 or 6,000 RPM, and preferably from about 1,100 to about1,300 RPM. Generally, the drive motor can be of any horsepower and isdesirably from about 1/100 to about ½ horsepower, with 1/12 horsepowermost preferred. Drive motor 905 can contain a fan (not shown) within themotor housing or immediately adjacent thereto to draw air through themotor thereby cooling the same. Power is conveyed from the motor throughmotor shaft 906 to drive wheel, not shown, which desirably has a varietyof grooves and/or teeth therein to receive a belt such as drive belt909. The drive belt can generally be of any suitable composition, suchas rubber or reinforced rubber which provides a long service life. Drivebelt 909 is connected to compressor pulley 910 which has a plurality ofgrooves and/or teeth therein. Optionally, an idler arm (not shown) canbe utilized to keep tension on the drive belt. Compressor pulley 910 isconnected to crankshaft 911. Although the present invention is onlyshown with a single reduction, it is conceivable to add more pulleys andreducing gearing. The single reduction utilized by the present inventionis lighter and more compact and contains fewer parts than an assemblyutilizing more than one reduction.

The radial multi-stage compressor of the present invention can have anynumber of pistons, such as from 2 to about 12, desirably from about 3 toabout 8 or 10, with about 5 being preferred. As shown in FIGS. 11 and12, the preferred embodiment contains 5 pistons 915, 916, 917, 918, and919, that is the first through fifth pistons respectively, radiallyarranged around crankshaft 911. Each piston is located within separatecylinders 925, 926, 927, 928, and 929 with first piston 915 located infirst cylinder 925, etc. As can be seen in FIG. 11, the pistons andcylinders or various portions thereof, have different shapes, and sizes,such as diameters, and lengths, in order to facilitate the gradual orstep-wise build-up of pressures from the first cylinder through the lastor fifth cylinder. For example, first piston 915 and second piston 916have a top and base which are integrally formed from a single element,and generally have the same diameter. The third piston 917, fourthpiston 918, and fifth piston 919, each have top portions which aresmaller than the base portions thereof. Inasmuch as each subsequentpiston is located on essentially the opposite side of the housing, theforces exerted on the various pistons by the crankshaft and theexpanding air in the cylinders are generally balanced and result in theefficient transfer of energy. Moreover, the radial design results in alightweight housing, which can be made of aluminum.

The radial compressor is designed so that the volume of gas is reduced,desirably proportionally, in each succeeding piston/cylinder assembly.Thus, as can be seen in FIG. 11, the compressible area 935 of the firstpiston/cylinder assembly is larger than the compressible area 936 of thesecond piston/cylinder assembly, and so on. The compression ratio cangenerally range from about 1 to about 10, and is preferably from about 2to about 5, with about 2.5 being most preferred. Motor 905 drivesannular crankshaft 911 which drives master connecting rod 920, as wellas slave connecting rods 921 through 924 each operably connectedthereto. The crankshaft has an offset thereon to allow reciprocation ofthe pistons.

The operation of the radial compressor generally is as follows: Drivemotor 905 through, drive belt 909, and pulley 910 rotates crankshaft 911and thus operably causes first through fifth pistons 915-919 toreciprocate and compress a source gas in their respective chambers. Morespecifically, a gas, which is preferably enriched oxygen gas is fed tothe first piston 915. The gases which are fed or supplied to the radialcompressor can be supplied from various sources, herein incorporated byreference, such as molecular sieve oxygen concentrator, a product tankor a buffer tank. Alternatively, gases from liquid or a high pressureoxygen cylinder which is typically too large and heavy to be easilymoved, can serve as a source gas which is fed to the compressor. Theselarge cylinders contain a wide range of oxygen therein, such astypically from about 800 to about 900 cubic feet of compressed orliquefied oxygen therein.

The piston/cylinder assemblies in each cylinder head containconventional check valve members such as ball and spring assemblies suchas those set forth in FIG. 8 which permit a gas to flow in and out ofthe piston/cylinder assembly in a desired fashion, i.e. one direction.The preferred check valve member of the present embodiment has a springrated preferably at 2 psi or less. In order to ensure the compressedconcentrated oxygen does not flow from a subsequent compression cylinderback into a prior cylinder, each cylinder head assembly will contain twooutlet check valves located sequentially with respect to one another asdiagrammically shown in FIG. 14.

FIGS. 11 and 12 show various fittings and piston head assembliescontaining check valves. Inlet check valve 940 of the first pistonassembly permits the gas to enter first compressible area 935 and outletcheck valves 941 permits the compressed gas to exit the first piston.The check valves permit the flow of gas in one direction so that oncethe gas is admitted to the first piston, it cannot be forced back outthrough the inlet check valve during the compression stroke of thepiston. Similarly, once forced out of the first piston, outlet checkvalves 941 prevents gas form being sucked in during the intake stroke ofthe first piston. In a similar manner, second piston 916 has an inletcheck valve 942 which permits the compressed gas from the firstpiston/cylinder assembly to be drawn into the second compressible area936, but prevents it from being forced back into the first piston.Outlet check valves 943 prevents the gas compressed in the secondpiston/cylinder assembly from being drawn back into the same once it hasbeen expelled therefrom.

In yet a similar manner, third piston 917 has an inlet check valve 944which permits the compressed gas from the second piston/cylinderassembly to be drawn into the third compressible area 937, but preventsit from being forced back into the second piston. Outlet check valves945 prevents the gas compressed in the third piston/cylinder assemblyfrom being drawn back into the same once it has been expelled therefrom.

In a similar manner, fourth piston 918 has an inlet check valve 946which permits the compressed gas from the third piston/cylinder assemblyto be drawn into the fourth compressible area 938, but prevents it frombeing forced back into the third piston. Outlet check valves 947prevents the gas compressed in the fourth piston/cylinder assembly frombeing drawn back into the same once it has been expelled therefrom.

Finally, in a similar manner, fifth piston 919 has an inlet check valve948 which permits the compressed gas from the fourth piston/cylinderassembly to be drawn into the fifth compressible area 939, but preventsit from being forced back into the fourth piston. Outlet check valves949 prevents the gas compressed in the fifth piston/cylinder assemblyfrom being drawn back into the same once it has been expelled therefrom.As shown in FIG. 14, appropriate tubing able to withstand high pressuressuch as metal tubing, connects various parts of the oxygen distributiondevice such as the various piston/cylinder assemblies, the buffer tank,the various regulators, the storage cylinder, etc., in a conventionalmanner known to those skilled in the art.

As shown in FIG. 11, each sequential piston cylinder assembly is notlocated adjacent to the next higher pressurizing piston cylinderassembly in a circumferential direction around the compressor, but isstaggered or offset from one another by at least one piston cylinderassembly so as to balance the forces on the compressor and thecrankshaft. In other words, each succeeding piston cylinder assemblywith respect to increasing the pressure of the enriched oxygen from theprevious assembly is located at least two assembly positions away in acircumferential direction so that there is desirably at least oneintervening piston cylinder assembly between each set or pair ofsequentially or succeeding pressure piston cylinder assemblies.

As concentrated oxygen is fed to the radial compressor, the firstcylinder will gradually build up a pressure, with the second cylindergradually building up a higher pressure, etc. until a desirable pressureis reached in storage cylinder 1000. While the ranges in each cylindercan vary widely, the desired range from the concentrator or other oxygensource as from about 2 to about 20 psig is approximately 34 psig. Thesecond compressor will gradually build up to a pressure of approximately110 psig with a third compressor gradually building up to a pressure ofapproximately 300 psig. The fourth compressor will gradually build up toa maximum pressure of about 800 psig whereas the last or fifthcompressor will build up to a maximum pressure of approximately 2,000psig. The above pressures are generally relative for a desired pressureof about 2,000 psig and of course will vary proportionally for a fivestage compressor with regard to any other desired end pressure such asabout 1,500 psig, 2,500 psig, 3,000 psig, etc. Generally, cylinder 1000can accept pressures in a range generally from about 500 to about 4,000psig, desirably from about 1,500 psig to about 3,000 psig, andpreferably from about 1,900 psig to about 2,100 psig.

The compressed gas is then fed through connector check valve 950 into agas storage cylinder 1000 through appropriate tubing, connectors,valves, and the like. These storage cylinders can generally be of anyconventional size with standard sizes such as M6, C, D, and E, beingsuitable. Typically, the gas cylinder can hold a volume of compressedgas in a range generally from about 10 to about 650, desirably fromabout 50 or 100 to about 400 or 500, and preferably from about 150 toabout 250 liters. Desirably, the cylinder has a built in pressure gaugeof from about 0 to about 3,000 psig, and is equipped with aself-contained release valve as well as a high pressure rupture disk setfor any desirable pressure such as about 6,000 psig. It can also have ahose barb outlet for connection to a patient cannula.

As stated above, the radial compressor 900 can be substituted directlyfor compressor assembly 100, that is in association with an oxygenconcentrator, and with various flow schemes, designs, etc., whetherpreferably prioritized to insure that a patient receives a requiredamount of oxygen-enriched gas, or not prioritized. Accordingly, the flowdiagram of FIGS. 2, 3, or 4 can be utilized but it is to be understoodthat generally any other flow system can also be utilized to route theenriched oxygen from product tank 30 either directly or indirectly,etc., to radial compressor 900.

The oxygen distribution system or device of the present inventioncontaining the radial compressor is diagrammically shown in FIG. 14. Theoxygen distribution device generally comprises oxygen sensor 860,reservoir or buffer tank 875, to accumulate or store the concentratedoxygen, the radial multi-stage compressor 900, high pressure switch 880,pressure gauge 835, output oxygen fitting or connector 845, portablehigh pressure cylinder 1000. Also included is flow regulator 877 andflow meter 830. As apparent from FIG. 14, the oxygen device alsocontains a test mode aspect, explained in greater detail hereinbelow, todetermine at least the concentration of the oxygen from an oxygenconcentrator, a large oxygen cylinder, or other source, before it isconnected to the oxygen device. While oxygen distribution device 800 isassigned primarily for home use, it can also be used in otherinstitutions such as nursing homes, clinics, hospital rooms, offices,and the like. As noted, the oxygen distribution device can receivevarious levels of concentration of oxygen such as at least about 50% or75%, and desirably at least about 80%. However, with respect to thepresent invention, the oxygen device is generally designed to receive atleast about 85%, and preferably at least about 90% oxygen and morepreferably about 93% by volume plus or minus 3%.

Once the level of oxygen concentration from the oxygen concentrator,etc., has been determined by the test mode system to meet thepredetermined, minimum requirement or level, the oxygen source such as aconcentrator is attached to oxygen inlet 820. From there a small portionis fed to oxygen sensor 860 which continuously monitors the oxygenconcentration. The remaining great majority of the oxygen is fed to areservoir or buffer tank 875 whereafter it is channeled into two flowstreams with a selected or predetermined portion of oxygen such as fromabout 1 to about 3, 4, or 5 and preferably about 2 liters per minutebeing fed to the compressor and with a selected or predetermined portionsuch as from about 0.1 to about 6, desirably from 1 to about 0.5 toabout 5, and preferably from about 1 to about 3 liters per minute,flowing to a patient. These two portions naturally add up to the totalamount or flow of oxygen from the reservoir of buffer tank 875; that isone flow stream such as that to the patient is the difference of theflow stream going to the compressor based upon the total flow or amountof oxygen exiting from the buffer tank. The oxygen distribution systemof the present invention is prioritized in that the radial compressorwill only run when oxygen sensor 860 determines that the oxygenconcentration is at or above a minimum predetermined level, for example90% by volume. Thus, should the oxygen concentration drop below thepredetermined level during operation of the compressor, sensor 960 willshut off the compressor until the concentration reaches thepredetermined level. However, while the compressor is shutoff to buildup the oxygen level, the enriched oxygen is continuously fed to thepatient. As apparent from FIG. 14, the enriched oxygen from the buffertank passes through pressure regulator 877 and flow meter 830. Pressureregulator 877 is set at any desired predetermined pressure level such asanywhere from about 1 to about 5 and desirably about 3 psig. The flowmeter can be set by the patient, or by any other competent medicalperson such as a physical therapist, medical doctor, etc. to a desiredflow rate.

The oxygen being fed to the compressor, as previously indicated, goesthrough a series of compression stages or cylinders with each subsequentstage pressurizing the gas to a higher pressure until finally the laststage achieves the desired indicated pressure whereupon cylinderpressure switch 880 will turn off compressor motor 905. As a safetybackup, burst disk 884 is provided to prevent an undue buildup ofpressure within the storage cylinder.

Generally, the only requirement required by the patient in operating theoxygen distribution device of the present invention is to turn on powerswitch 840 and to set flow meter to desired rate as determined by amedical person or the like.

Referring to FIG. 14, the device 800 may also advantageously include anoxygen concentration testing function. This test mode system includesthe test mode inlet 815. The inlet 815 communicates with the oxygensensor 860 through a check valve 854 whose downstream side is incommunication with the downstream side of a check valve 872 thatnormally passes gas from the normal mode inlet 820. The downstream sidesof the check valves 854, 872 are both in communication with a flowrestrictor 856 which limits the flow of gas to the oxygen sensor 860.The check valve 872 prevents the flow of gas from the test mode inlet815 toward the normal mode inlet 820. The check valve 854 prevents theflow of gas from the normal mode inlet 820 toward the test mode inlet815.

A test pressure switch 852 senses the pressure of gas applied to thetest mode inlet 815. The switch 852 provides an indication thatpressurized gas is being applied to the test mode inlet 815. The switch852 may, for example, be actuated by a gas pressure of 2.1 psi orgreater.

Upon indication of pressurized gas being applied to the test mode inlet815, the compressor 900 is disabled and the oxygen sensor 860 is thenused to test the oxygen level or concentration of the gas applied to thetest mode inlet 815.

Referring to FIG. 15, the operation of the device 800 may, for example,be advantageously controlled by a controller 1100. The controller 1100is most preferably a microcontroller, but may be, for example, amicroprocessor with associated memory and input/output circuitry, anapplication specific integrated circuit, a field programmable gatearray, or other suitable programmable device.

The controller 1100 receives inputs from the oxygen sensor 860, the highpressure switch 880 and the test pressure switch 852 and providesoutputs to the compressor 900 and the indicators 1102, 1104, 1106, 1108,1110. The controller 1100 may also, for example, incorporate thepreviously mentioned control means 50. The indicators 1102, 1104, 1106,1108, 1110 may be, for example LEDs, light bulbs, an LCD screen, orother suitable indicators, including, for example, audible indicators.

When the power switch 840 is first turned on, the FULL indicator 1102,the WAIT indicator 1104, the FAULT indicator 1106 and the TEST indicator1108 will come on for a short time (e.g., 1 second) to provide anindication that these indicators are functioning. Then the indicators1102, 1106, 1008 will go off.

The WAIT indicator 1104 will remain on long enough for the oxygen sensor860 to reach operating temperature (e.g., 3.0 minutes).

The controller 1100 also monitors the heater current and voltage and theoutput current voltage of the oxygen sensor 860 whenever the device 800is turned on. If a fault in the oxygen sensor 860 is detected at anytime, the WAIT indicator 1104 is flashed at a one second rate, the FAULTindicator 1106 is activated and all other indicators are deactivated. Inthis state, the compressor 900 and the test mode function will notoperate.

If no gas pressure is detected by the test pressure switch 852, thedevice 800 will operate in normal mode. That is, if there is anacceptable level of oxygen as sensed by the oxygen sensor 860 in the gasapplied to the normal mode inlet 820 (e.g., greater than 91 percent) thecompressor 900 will run and the FILLING indicator 1110 will beactivated. If the high pressure switch 880 is activated, the FULLindicator 1102 will be activated, the FILLING indicator 1110 will bedeactivated and the compressor 900 will be deactivated by the controller1100.

If the high pressure switch 880 is activated during the warm up period(e.g., a full bottle (e.g., 2,000 psi) already attached to the oxygenoutlet 825), the FAULT indictor 1106 will be flashed at a one secondrate by the controller 1100 and the device 800 must be reset to operate.

If the test pressure switch 852 detects gas pressure at the test modeinlet 815, the device 800 will operate in test mode. If the gas pressureat the inlet 815 is removed, the device 800 will again operate in normalmode.

Whenever the device 800 enters or leaves test mode, the controller 1100will bsuspend the operation of the device 1100 for a period of time(e.g., 30 seconds) and activate the WAIT indicator 1104 to allow theoxygen sensor 860 time to stabilize with a new input gas.

In test mode, the controller 1100 will disable the compressor 900,activate the TEST indicator 1108 and use the oxygen sensor 860 to testthe oxygen level of the gas applied to the test mode inlet 815. If thereis an acceptable level of oxygen, the controller 1100 will activate theFULL indicator 1102. Otherwise, the controller 1100 will activate theFAULT indicator 1106.

The test mode of operation permits a user to conveniently check theoxygen content of a cylinder or concentrator output without activatingthe compressor of the device. The user activates the test mode by merelyconnecting a gas source to the test mode inlet. Normal operation resumeswhen the gas source is removed. The user is not required to perform anyother operation. This is particularly advantageous for impaired,unsophisticated or technology intimidated users.

The radial compressor and assembly comprising connecting tubing etc. iscompact and light, approximately % the size of compressor assembly 100shown in FIG. 8, and approximately ¼ the weight thereof. Advantageously,the radial compressor of the present invention can be utilized with anycommercially available oxygen concentrator and has a unitizedconstruction and compact design for easy placement and storage. Theradial compressor of the present invention is very efficient withrespect to power consumption, is quiet when running, and produces verylittle vibration. Moreover, while the consumption of power is low, theunit has generally the same features as other units such as in FIGS.1-10, for example, the same fill time.

Another embodiment of the present invention, similar to that shown inFIGS. 11 through 15, is set forth in FIGS. 16, 17, and 18 which feedsenriched oxygen primarily to a patient and secondarily to a buffer tankand then to a radial compressor. Unless specified hereinbelow, theembodiments of FIGS. 16, 17, and 18 are generally the same as that setforth in FIGS. 11 through 15 as described hereinabove and hereby fullyincorporated by reference. It is also to be understood that allpressures in this specification relate to pressures above atmospherepressure, that is 5 psi is 5 pounds per square inch gauge. In theembodiment of FIGS. 16 through 18, enriched oxygen from an oxygen orproduct storage tank is fed through two different outlets or lines, oneline directed to the patient and the other line connected to a buffertank. The buffer tank flow line contains oxygen-enriched gas at apressure generally that of the storage tank whereas the patient flowline feeds the oxygen-enriched gas at a reduced, low pressure to thepatient. The apparatus utilizes two different and independentcompressors, an initial compressor for compressing air and feeding it tomolecular sieves for enriching or concentrating to a high amount ofoxygen by volume and a second compressor, which operates independentlyof the first, for compressing the oxygen-enriched gas to a very highpressure for delivery to a high pressure storage cylinder. That is, thesecond, e.g. a radial, compressor is operated by a power source, e.g. amotor, engine, other than by the oxygen enriched gas as compresses bythe first compressor (such as in a pressure intensifier). As with theprevious embodiments, the embodiment of FIGS. 16 through 18 prioritizesthe oxygen-enriched gas so that flow is always continuous to the patientand optional to the buffer tank.

A description of the apparatus for compressing and storing anoxygen-enriched gas is as follows. Initial or concentrator compressor1205 receives air from the atmosphere and through flow line 1207 feedsit to oxygen concentrator 1210. The concentrator can be any conventionalor standard concentrator known to the art and to the literature, or asdescribed hereinabove. Such a concentrator is commercially availablefrom Invacare Corporation, Elyria, Ohio as models 5LX and 5LX02.Typically, such oxygen concentrators, through the use of molecularsieves, enriches the oxygen to a desirable level such as at least about50% or 75%, desirably at least about 80%, and preferably at least about85% or 90%, more preferably about 93% by volume plus or minus 3%. Theoxygen-enriched gas is fed through product tank flow line 1215 to oxygenproduct storage tank 1220. Pressure in the storage tank is generally thesame as generated by the oxygen concentrator and can vary as from about15 to about 20 or 22 psi. Storage tank 1220 primarily acts as a holdingtank for feeding the oxygen-enriched gas to the patient but alsoprovides oxygen-enriched gas to a buffer tank which then is fed to asecond independent compressor, which operates independently of theoxygen concentrator compressor, and subsequently to a high-pressurestorage cylinder.

Integral with oxygen storage tank 1220, is pressure regulator 1225 whichserves to reduce the oxygen-enriched gas to any desirable pressure forflow to patient flow meter 1235 through patient flow line 1230.Accordingly, the pressure regulator emits oxygen-enriched gas from theproduct storage tank to a first outlet such as line 1230 at a reduced orlow pressure. While pressure regulator 1225 can be located on or in anyportion of the storage tank, it is conveniently an integral part of thestorage tank lid or cap. That is, concentrated or oxygen-enriched gaswithin the product storage tank before exiting the same is fed to thepressure regulator 1225 which reduces the pressure to a desirablepredetermined low pressure such as from about 3 or 4 to about 10 psiwith a desired pressure being about 4 to about 6 or 8 psi and preferablyabout 5 psi. The oxygen-enriched gas is then fed to patient flow meter1235 where, as in the prior embodiments, it can be adjusted to any flowrate such as from about 0.1 or 1.0 to about 3, 5, or 6 liters perminute. Flow meter 1235 can be adjusted by a patient, or by a physicaltherapist or other medical personnel.

An oxygen sensor can be located either within oxygen concentrator 1210or, as shown, on patient flow line 1230 as oxygen sensor 1233. Whenlocated in the oxygen concentrator, the sensor measures the level of theoxygen by volume in the gas and if it is below a predetermined range, asafety warning such as by a light, buzzer, etc. is activated warning thepatient or user of the low oxygen-enriched gas value. This prevents apatient from utilizing the oxygen concentrator if the oxygen value istoo low. Alternatively, when located on patient flow line 1230, thesensor also monitors the level of the oxygen in the gas to ensure thatthe concentration is above a predetermined value. Otherwise, a safetywarning such as a light, buzzer, etc. is activated to warn the patientof low oxygen condition.

An independent or separate second outlet feeds oxygen-enriched gas fromthe oxygen or product storage tank to buffer tank 1240 through buffertank flow line 1245. The pressure of the oxygen-enriched gas of thesecond outlet is independent of and is greater than the low pressure ofthe first outlet and generally is at the pressure of product storagetank 1220. Desirably, the moderate pressure in buffer flow line 1245 isfrom about 10, 12 or 15 to about 20 or 22 psi.

Flow restrictor 1249 located in buffer tank flow line 1245 serves tolimit the flow of the oxygen-enriched gas so that a sufficient amount isgenerally always available for the patient and the remaining amount,which often is small, is fed solely to the buffer tank, etc. Flow line1245 also contains an oxygen sensor 1248 which continuously monitors theconcentration of the oxygen. The concentration of oxygen to the buffertank is maintained at a predetermined level or set point, typically 93%oxygen by volume plus or minus 3%. If sensor 1248 detects a value lowerthan the predetermined set point, the electronics of the apparatus aredesigned to shut off compressor 1250. Stopping the radial compressorpermits the oxygen concentrator to process air at a slower rate thusresulting in an increased oxygen concentration or purity so that thepredetermined oxygen concentration such as about 93% oxygen by volumecan once again be quickly achieved.

The right-hand side of FIG. 16 relating to the buffer tank, thecompressor and the high pressure storage cylinder, etc. is furtherdetailed in FIG. 17.

Buffer tank 1240 acts as a holding tank for the oxygen-enriched gaswhich is fed to compressor 1250 via line 1255. While compressor 1250 canbe any conventional compressor as opposed to a pressure intensifier, itpreferably is a radial compressor as described hereinabove andaccordingly fully incorporated by reference, wherein like numbersdescribe like parts. Through the various stages, such as set forthabove, the oxygen-enriched gas is compressed in stages until a suitableend stage emits the oxygen at a pressure for storage in high pressurestorage cylinder 1260. After being compressed by the radial compressor,and once a sufficient amount of oxygen-enriched gas has been fed to highpressure storage cylinder 1260 to achieve a desired predeterminedpressure, pressure switch 880 will automatically turn off compressor1250. Pressure gauge 835 also exists as a visual indication of theamount of pressure in cylinder 1260. Check valve 885 preventsoxygen-enriched gas from flowing out of the high cylinder 1260 wheneverthe compressor is not being operated. As a safety backup, burst disk 884is provided should for some reason the automatic high pressure switch880 not turn off compressor 1250 at a predetermined high pressure level.

As noted in the prior embodiment with regard to the radial compressorsetup, the pressure of high pressure storage cylinder 1260 can be anydesired or predetermined pressure. While the desired pressure ofcylinder 1260 is approximately 2,000 psi, it can range from about 500 toabout 4,000 and desirably from about 1,500 to about 3,000 and preferablyfrom about 1,900 to about 2,100 psi.

The advantage of the embodiment of FIGS. 16 and 17 is that independentand different pressures from the product storage tank can be utilizedwith the pressure component fed to the buffer tank secondcompressor-etc. being greater and independent of the component fed tothe patient. The second or radial compressor 1250 operates independentlyof compressor 1205 which feeds air to the oxygen concentrator.

Referring to FIG. 18, the operation of apparatus 1200 can be operated bya controller in a manner as described hereinabove with regard to FIGS.11 through 15. Thus, controller 1100 preferably is a microcontroller,but can be, for example, a microprocessor with associated memory andinput/output circuitry, an application specific integrated circuit, afield programmable gate array, or other suitable programmable device.

Controller 1100 receives inputs from oxygen sensor 1233 or theconcentator oxygen sensor, and high pressure switch 880 and providesoutputs to the compressor 1250 and the indicators 1102, 1104, 1106,1108, 1110. The controller 1100 may also, for example, incorporate thepreviously mentioned control means 50. The indicators 1102, 1104, 1106,1108, 1110 may be, for example LEDs, light bulbs, an LCD screen, orother suitable indicators, including, for example, audible indicators.

When the power switch 840 is first turned on, the FULL indicator 1102,the WAIT indicator 1104, the FAULT indicator 1106 and the TEST indicator1108 will come on for a short time (e.g., 1 second) to provide anindication that these indicators are functioning. Then the indicators1102, 1106, 1008 will go off.

The WAIT indicator 1104 will remain on long enough for the oxygen sensor1233 or the concentrator oxygen sensor to reach operating temperature(e.g., 3.0 minutes).

The controller 1100 also monitors the heater current and voltage and theoutput current voltage of the oxygen sensor 1233 or the concentratoroxygen sensor whenever device 1200 is turned on. If a fault in theoxygen sensor 1233 or the concentrator oxygen sensor is detected at anytime, the WAIT indicator 1104 is flashed at a one second rate, the FAULTindicator 1106 is activated and all other indicators are deactivated. Inthis state, the compressor 1250 and the test mode function will notoperate.

If there is an acceptable level of oxygen as sensed by the oxygen sensor1233 or the concentrator oxygen sensor in the gas applied to the normalmode inlet 1215 (e.g., greater than 90%) the compressor 1250 will runand the FILLING indicator 1110 will be activated. If the high pressureswitch 880 is activated, the FULL indicator 1102 will be activated, theFILLING indicator 1110 will be deactivated and compressor 1250 will bedeactivated by the controller 1100.

If oxygen sensor 1248 detects an acceptable predetermined level ofoxygen, radial compressor 1250 will be allowed to operate. However,should oxygen sensor 1248 detect an amount of oxygen below apredetermined level, the controller will automatically close down orstop the operation of radial compressor 1250. After the oxygenconcentration is increased to above the predetermined level, radialcompressor 1250 will once again allow it to be operated.

If the high pressure switch-880 is activated during the warm up period(e.g., a full bottle (e.g., 2,000 psi) already attached to the oxygenoutlet 825), the FAULT indictor 1106 will be flashed at a one secondrate by the controller 1100 and the device 1200 must be reset tooperate.

The test mode operation is based upon a value of pressure being presentin a test fitting. If the pressure of the gas stream at the test inletis greater than some predetermined value, then the controller 1100should temporarily suspend any operation of the radial compressor andthen wait a predetermined time (typically 30 sec.) for the gas values tostabilize. Once the timeout period is over, the controller then usesoxygen sensor 1248 to determine whether the feed gas used by the radialcompressor for filling the high pressure tank is above a predeterminedconcentration value.

The operation of the test mode is basically the same whether or not theunit enters or exits the test mode. There is always a delay to make surethe gas stream is within the requirements of the minimum values ofoxygen concentration for filling the high pressure tank or testing thegas value in the test mode. This delay is included to make sure the gasstream reaches full value with any change in sources of the gas withinthe internal plumbing of the system.

Test switch 852 can be either a preset value for a mechanical, pressureoperated switch or it can be a pressure sensor on the board thatprovides an electrical value for the gas pressure present on the testfitting. The main purpose of test switch 852 is to continuously monitorthe oxygen concentration of the feed gas for the radial compressor tomake sure it is within the requirements of the predetermined oxygenconcentration percentage.

While in accordance with the patent statutes the best mode and preferredembodiments have been set forth, the scope of the invention is notlimited thereto, but rather by the scope of the attached claims.

1. An apparatus for supplying oxygen-enriched gas to a patient and to ahigh pressure storage tank, comprising: a first compressor whichreceives ambient air; an oxygen concentrator which produces oxygenenriched gas, said oxygen concentrator having an inlet which receivesair from said first compressor and an outlet which provides oxygenenriched gas to a product storage tank; a first outlet flow line whichoperatively delivers said oxygen enriched gas from said product tank toa patient, said flow line having a pressure from about 3 to about 10psi; a second outlet flow line which operatively delivers said oxygenenriched gas from said product tank to a buffer tank at a pressure fromabout 12 to about 22 psi, said buffer tank operatively connected by aflow line to a radial compressor, said radial compressor being capableof compressing said oxygen enriched gas and transferring the oxygenenriched gas to a high pressure storage tank, and a prioritizingapparatus which terminates the operation of said radial compressor whenthe oxygen concentration of said oxygen enriched gas operativelydelivered to said radial compressor falls below a predetermined value sothat said oxygen enriched gas is continuously supplied to the patient.2. An apparatus according to claim 1, wherein the amount of said oxygenin said patient flow line is at least 80% by volume.
 3. An apparatusaccording to claim 2, wherein said radial compressor includes at leasttwo piston cylinder assemblies radially arranged around a crank shaft,and said piston cylinder assemblies adapted to sequentially compresssaid oxygen-enriched gas from said first piston assembly through saidlast piston assembly.
 4. An apparatus according to claim 3, wherein saidprioritization includes a determination of said oxygen-enriched gasoperatively delivered to said radial compressor by an oxygen sensor andthe operation of said radial compressor being terminated when saidsensed oxygen-enriched gas is below a predetermined oxygen level, andwherein said patient oxygen-enriched gas and said high pressure storagetank has an oxygen concentration of at least 90% by volume.
 5. Aapparatus according to claim 4, wherein said radial compressor isoperated by a power source other than said oxygen-enriched gas from saidoxygen concentrator.
 6. An apparatus for supplying oxygen-enriched gasto a patient and to a high pressure storage tank, comprising: a lowpressure, oxygen-enriched gas patient flow line for use by a patient; aseparate moderate pressure, oxygen-enriched gas buffer flow lineoperatively connected to a buffer tank; said moderate pressure beinggreater than said low pressure; said patient flow line and said buffertank flow line being prioritized so as to continuously supply saidoxygen-enriched gas for use by a patient; a radial compressor operatedby a power source other than said oxygen enriched gas, said buffer tanksolely and operatively connected to said radial compressor; said radialcompressor being capable of compressing said oxygen-enriched gas to ahigh pressure; and a high pressure storage tank for portable storage ofsaid high pressure oxygen-enriched gas.
 7. An apparatus according toclaim 6, wherein said radial compressor includes at least two pistoncylinder assemblies radially arranged around a crank shaft, and saidpiston cylinder assemblies adapted to sequentially compress saidoxygen-enriched gas from said first piston assembly through said lastpiston assembly.
 8. An apparatus according to claim 7, wherein theamount of said oxygen in said patient flow line is at least 80% byvolume, and wherein said prioritization includes a determination of theoxygen-enriched gas operatively delivered to said radial compressor byan oxygen sensor and the operation of said radial compressor beingterminated when said sensed oxygen-enriched gas is below a predeterminedoxygen level.
 9. An apparatus according to claim 8, wherein said patientoxygen-enriched gas and said high pressure storage tank has an oxygenconcentration of at least 90% by volume, and wherein said patient flowline has an oxygen-enriched gas flow rate of from about 1 to about 6liters per minute.
 10. An apparatus according to claim 9, wherein thepressure in said patient flow line is from about 3 to about 8 psi,wherein the pressure of said oxygen-enriched gas in said buffer flowline is from about 10 to about 22 psi, and wherein said high pressurestorage tank is capable of storing said compressed oxygen-enriched gasat a pressure of from about 500 to about 4000 psi.
 11. An apparatusaccording to claim 7, including an oxygen product storage tank andwherein said patient flow line and said buffer tank flow line areindependently connected to said oxygen product storage tank.
 12. Anapparatus according to claim 6, wherein said high pressure storage tankis portable.
 13. An apparatus according to claim 8, wherein said highpressure storage tank is portable.
 14. An apparatus according to claim10, wherein said high pressure storage tank is portable.
 15. A processfor supplying oxygen-enriched gas to a patient and to a high pressurestorage tank, comprising the steps of: continuously supplying lowpressure oxygen-enriched gas through a patient flow line; separatelysupplying a moderate pressure, oxygen-enriched gas through a buffer tankflow line to a buffer tank; said moderate pressure being greater thansaid low pressure; operatively supplying said oxygen-enriched gas fromsaid buffer tank to a radial compressor and feeding said compressedoxygen-enriched gas to a high pressure storage tank; and prioritizingsaid patient flow line and said buffer tank flow line so that saidpatient flow line is continuously supplied with said oxygen-enrichedgas.
 16. A process according to claim 15, wherein the oxygenconcentration in said patient flow line and said buffer tank flow lineis at least 75% by volume.
 17. A process according to claim 16, whereinthe pressure of said oxygen-enriched gas in said storage tank is atleast 500 psi, wherein said radial compressor includes at least twopiston cylinder assemblies radially arranged around a crank shaft, andsaid piston cylinder assemblies adapted to sequentially compress saidoxygen-enriched gas from said first piston assembly through said lastpiston assembly.
 18. A process according to claim 17, wherein thepressure of said oxygen-enriched gas in said patient flow line is fromabout 3 to about 10 psi and wherein the pressure of said oxygen-enrichedgas in said buffer tank flow line is at a higher pressure.
 19. A processaccording to claim 18, wherein said prioritization includes shutting offsaid radial compressor when said oxygen-enriched gas thereto is below apredetermined level.
 20. A process according to claim 19, wherein thepressure of said oxygen-enriched gas in said high pressure storage tankis at least 1500 psi, and wherein the oxygen concentration in saidpatient flow line and said buffer tank flow line is at least 90% byvolume.
 21. A process according to claim 15, wherein said high pressurestorage tank is portable.
 22. A process according to claim 17, whereinsaid high pressure storage tank is portable.
 23. A process according toclaim 18, wherein said high pressure storage tank is portable.
 24. Aprocess according to claim 20, wherein said high pressure storage tankis portable.